The well-known nonrelativistic connection that gives a hadron's charge density as the Fourier transform of the charge form factor is not justified relativistically. The question becomes how one could obtain a relativistically correct charge density from the lepton scattering data. A by now older suggestion [1]}, [2]} is to work in the light front formalism, or in an infinite momentum frame, with the hadron and virtual photon traveling in essentially opposite directions and where one can think of the hadron as flattened in its direction of motion. It is then possible to obtain a relativistically well defined area charge density by projection onto the transverse plane, both for polarized and unpolarized situations.
